I have the following Transact SQL query using a union. I need some pointers as to how this would look in LINQ i.e some examples wouldbe nice or if anyone can recommend a good tutorial on UNIONS in linq.

select top 10 Barcode, sum(ItemDiscountUnion.AmountTaken) from
(SELECT d.Barcode,SUM(AmountTaken) AmountTaken
  FROM [Aggregation].[dbo].[DiscountPromotion] d

  GROUP BY d.Barcode

  UNION ALL

  SELECT i.Barcode,SUM(AmountTaken) AmountTaken
  FROM [Aggregation].[dbo].ItemSaleTransaction i

  group by i.Barcode)  ItemDiscountUnion

  group by Barcode